The present invention relates generally to conveyors, and more particularly relates to pouring conveyors for mold handling systems.
Molded metal castings are commonly manufactured at foundries through a matchplate molding technique. This technique employs green sand molds comprised of prepared sand and additives that are compressed around cope and drag patterns mounted on opposite sides of a matchplate. The sand mold is thus formed in upper and lower matching portions, an upper cope mold, and a lower drag mold. The cope mold is formed in a separate cope flask that is filled with prepared sand and compacted onto the matchplate. The matchplate is the removed leaving an indentation in the cope mold of the desired shape for the upper portion of the casting. Simultaneously, the drag mold is formed in a separate drag flask. Usually the matchplate is in the form of a planar member with the pattern for the cope mold on one side and the pattern for the drag mold on the other. After the cope and drag molds have been formed, they are placed together to form a unitary mold having an interior cavity of the desired shape. The cavity can then be filled with molten metal through an inlet or xe2x80x9cspruexe2x80x9d provided in the cope mold to create the desired casting. Such a system is disclosed in Hunter, U.S. Pat. No. 5,022,212, the disclosure of which is hereby incorporated by reference in its entirety.
Once the mold is formed, the mold is then placed into a mold handling system through which various steps are performed to achieve the desired metal castings. After leaving the mold-making machine, the molds are carried on pallets through a weight and jacket installation station. There, supportive weights and jackets are installed on the sand molds to provide support for the heavy molten material that will be received in the internal cavity of the mold. Molds are then conveyed through a pouring station where molten material is poured into the sand molds. The molten material is then conveyed further until sufficient cooling has taken place at which the weights and jackets are removed and recycled to the weight and jacket installation station for reuse. Thereafter, the molten material is cooled even further through an additional cooling station such as a cooling conveyor or a cooling carousel. Once the molten material is sufficiently hard and rigid, the sand molds are broken and the metal castings released. Mold handling systems are generally disclosed in U.S. Patents owned by the present assignee including: U.S. Pat. Nos. 4,589,467, 5,901,774, 5,927,374, 5,971,059, 6,145,577 and 6,263,952, the entire disclosures of which are hereby incorporated by reference in their entirety to illustrate some of the different arrangements for which the present invention may be applicable.
While the foregoing molding machines and their mold handling systems have met with substantial commercial success, they are not without drawbacks. One drawback existing in the art relates to the conveyor mechanism that transports molds on pallets through the pouring station. In particular, after molten metal material is poured into the molds at the pouring station, sometimes drops of molten metal material are inadvertently spilled onto the conveyor and the rollers of the conveyor (including the bearings of the rollers). This is undesirable and can cause operating problems and downtime for the conveyor.
In light of the above, it is a general objective of the present invention to remedy the problems associated with spillage of molten material on the conveyor at the pouring station of a molding machine.
In that regard, it is a further objective to keep the pallets carrying molds on the desired path through a mold handling system.
In accordance with these and other objectives, the present invention is directed toward a conveyor for a molding machine and a molding machine incorporating the conveyor in which the portion of the conveyor and its driven rollers that run through the pouring station have been shortened such that the pallets extend over the conveyor to shield the conveyor and rollers from molten material. In the preferred embodiment, these rollers are also slanted at an oblique angle relative to the intended path of the molds such that the driven rollers bias the pallets away from the pouring line to better ensure that pallets carrying molds do not wander laterally and fall off the conveyor onto the pouring line. Alternative biasing means are also disclosed and may be used.
A molding machine according to the invention comprises a sand mold forming station adapted to form a plurality of sand molds. The molds are carried on pallets through a pouring station downstream of the sand mold forming station. A cooling station is located downstream of the pouring station for cooling the material in the molds to form metal castings. A conveyor transports the molds on the pallets along a linear path through the pouring station. At the pouring station, molten metal is poured into the molds along one side of the conveyor (e.g. a pouring side or xe2x80x9cpouring linexe2x80x9d). The conveyor has rollers at the pouring station carrying the molds on the pallets. The rollers are driven by a motor to move the pallets and molds along the linear path. The pallets extend horizontally beyond the rollers toward the pouring line to shield and prevent molten material from being spilled onto the rollers. The rollers rotate about rotational axes that intersect the linear path at an oblique angle sufficiently large enough such that when the rollers are driven, the pallets are mobilized forwardly along the linear path with a bias away from the pouring line. This prevents pallets from falling off on the pouring side.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.